Abstract
This paper documents the ongoing design process of a Stirling engine prototype for a source temperature of 95 °C, aiming to achieve shaft power on the order of 100 Watts. The engine will serve to produce experimental data for the validation of a numerical low temperature Stirling model. The higher-level motivation is to assess the technical and economical potential of producing power from abundant sources of low temperature heat by using Stirling engines. Design decisions are governed by the goals of minimizing energy losses and maximizing the variability of operating points through variable heat exchanger geometry, compression ratio and charge pressure. The resulting design is a beta engine with a total gas volume around 100 liters. It features displacer and power pistons in a combined cylindrical working space and a mechanism using pivoting links similar to a bellcrank. The stroke of the power piston is adjustable while maintaining a constant top dead center position. A component critical for friction is the power piston seal, for which a low friction rolling seal and a conventional sliding seal were considered. As of June 2021, the development is at an advanced state and the first set of components are entering production.
Highlights
There is a significant energy resource in the form of low temperature (LT) heat that is widely available but currently not being utilized
A main research question to be tackled is the effect of different heat exchanger geometries and sizes on Low Temperature Difference Stirling Engines (LTDSEs) performance
All previous prototypes had their heat exchangers integrated into the engine body so that it was not possible to test different heat exchanger shapes in one engine
Summary
There is a significant energy resource in the form of low temperature (LT) heat that is widely available but currently not being utilized. This refers to heat sources with temperatures of 150 °C or lower. LT heat is commonly discarded as a by product of energy intensive industries These sources of sustainable energy have so far never played a role because their low exergy makes them inefficient to process compared to higher temperature sources. This causes their utilization to be not economically desirable compared with conventional sources. The as-built engine may be subject to only minor changes compared to the designs shown here
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